FreeShip newbie needs help

Discussion in 'Software' started by Shamkhan, Jan 27, 2021.

  1. Shamkhan
    Joined: Jan 2021
    Posts: 3
    Likes: 0, Points: 1
    Location: Switzerland

    Shamkhan New Member

    Greetings, Boat Design Veterans,

    I have just imported an outrigger sailing canoe from France to Switzerland, where I live. This 16 ft va'a, that roamed the Atlantic waters off Brittany, will hopefully cruise the turquoise waters of Lake Neuchâtel in spring - but until then, I have some issues with its registration.

    I need to calculate its seaworthiness, especially its buoyancy: I have to prove that even with the hull filled with water and an additional weight of 30kg, it won't sink. Unless I do this, I can't register it, but as long as it's not registered, I will be fined (a lot) if I try to do this on the water.

    So I have to calculate it on my own, but for that I need to calculate the volume of the hull as well as the volume of the air chambers at the bow and helm. Though he doesn't know those volumes himself, the builder gave me the FreeShip file he used to build the boat 15 years ago. The .fbm file doesn't contain the air chambers themselves, but I know how far away from the bow/helm they stop.

    Could anyone tell me if FreeShip can tell me the volume of a given central segment of the hull, so I can also deduce the volume of the air chambers at its extremities?

    Thanks in advance

    Shamkhan

    ibb.co/FxvFRNZ
     

    Attached Files:

  2. Olav
    Joined: Dec 2003
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    Location: Filia pulchra Lubecæ

    Olav naval architect

    Not too sure about the latest versions of FreeShip, but in the professional DelftShip version you can define tanks and have their volumes calculated. Also it would be easy to export the hull surfaces to another CAD system and have the volumes calculated there.

    I reckon there are watertight bulkheads in both the bow and the stern that separate the WT compartments from the helm area in the middle. If you tell me the position of these bulkheads I can easily give you the volumes you want to know.
     
  3. Heimfried
    Joined: Apr 2015
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    Location: Berlin, Germany

    Heimfried Senior Member

    Hi Shamkhan,
    I've got freeship but are not really able to deal with it. But this may be a hint:
    Pirogue_CH.jpg

    Freeship menu point is "Berechnungen" ("calculations"?).
     
  4. Shamkhan
    Joined: Jan 2021
    Posts: 3
    Likes: 0, Points: 1
    Location: Switzerland

    Shamkhan New Member

    Thank you!!! The front WT compartment stops 100cm from the bow and is 40cm high; the one at the back stops 110cm from the stern and is 38cm high. Both seem to go to the extremities of the hull.

    Heimfried seems to be right, the key element to calculate the total volume of the hull seems to be iunder hydrostatics, but which one is it?
     
  5. pafurijaz
    Joined: Dec 2016
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    Location: Italy

    pafurijaz Senior Member

    Here the file converted for you, into solid for Rhino and into IGES surfaces so now you can perform the necessary steps by your self with others CADs and the hull volume is 0,46 m^3
     

    Attached Files:

  6. Olav
    Joined: Dec 2003
    Posts: 319
    Likes: 46, Points: 38, Legacy Rep: 460
    Location: Filia pulchra Lubecæ

    Olav naval architect

    Okay,

    given the bulkhead heights larger than the hull depth at each station I did a small assumption and added a deck which seems to look typical for this kind of (outrigger) kayak.

    The volumes are:
    • 0.0645 m³ for the aft compartment (blue)
    • 0.0445 m³ for the bow compartment (red)
    • 0.5521 m³ for the fully enclosed hull (green)
    Due to the additional volume of the deck the result is somewhat larger than what Pa Furijaz came up with.

    @Shamkhan: I'm not familiar with the registration procedures for small pleasure craft on Swiss lakes. Do you need the calculation to be something "official" for the local authorities or do they accept some pen-and-paper calculations by "anybody" as long as it looks reasonable?

    Hope this helps.
     

    Attached Files:

    Last edited: Jan 29, 2021
    pafurijaz likes this.
  7. pafurijaz
    Joined: Dec 2016
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    Location: Italy

    pafurijaz Senior Member

    I think the difference is due to the bombed solid my is only flat on top upload_2021-1-27_20-9-54.png
     
    Olav likes this.

  8. Shamkhan
    Joined: Jan 2021
    Posts: 3
    Likes: 0, Points: 1
    Location: Switzerland

    Shamkhan New Member

    Thank you, Pa Furijaz and Olav, you really helped me out. I wish I knew how you did this.

    The employee with whom I spoke at the navigation office seemed to indicate the latter rather than the former. i still have to model the ama/floater for which I haven't got a 3d model yet, as its volume is part of the overall equation. I'll try and segment it into 10 stations and measure it and try to feed it into the software.
    You sure have a complex but fascinating work.
    Thank y'all so much for your time and your help :)
     
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